The file format of executable games created using GameMaker 8.1 has been cracked and a GameMaker 8.1 decompiler has been released.

Until now games created using GameMaker 8.1, which promised “new, more secure .EXE encryption”, were “safe” from having their source code revealed.

This latest release is actually an updated version of the original Game Maker 8 decompiler. I would imagine that the decompiler could quickly be rendered useless thanks to the system used by YoYo Games to push out regular updates to GameMaker 8.1 users. Or a more speedy game of cat and mouse could ensue.

Writing on Twitter prior to 8.1’s release GameMaker developer Mike Dailly described the new encryption as “nothing amazing” but added that it “should block things for a little while” and that he “could even change it with each release”.

The most recently released GameMaker decompiler was able to turn iOS apps released by YoYo Games into a computer editable Game Maker file. That was developed as a stepping stone in a project working towards developing a, subsequently abandoned, Game Maker iOS compiler which could attach YoYo Games’ iOS runner on to any editable Game Maker file.

31 Responses to GameMaker 8.1 Decompiler Released

Are you aware that sometimes the decompiled games have errors, or some features missing? I had to reconstruct quite a bit of one of my more complicated projects. Is there any way to fix that issue in a future release?

Blue :Obsfucating is not really the solution. There are (mainly) two kind of people who decompile games(or better people have 2 kind of intentions with decompiling):
1 — They decompile your game because they are interested in how you made your game, and want to learn.
2 — They decompile your game, edit it, and release it, as if it was their own.
I don’t see the second one a lot, but they exist.

For this reason, I always like to hide additional credits in my projects where most people would never find them. Usually the types of people who do this aren’t intelligent enough to make their own complex games, which also usually means that even if they knew I had hidden credits somewhere else in the file, they wouldn’t be able to find them.

This is by no means a method of prevention, though it is nice to be able to prove to people after this occurs that someone’s work is not their own, without the need to bother scrambling to provide old topics and dates as evidence.

God d**n it! I lost the usb stick where I was storing the source code of my game and now that I learn there’s a decompiler for GM8.1 there are no links anywhere!!! How am I supposed to make sure this decompiler works if there isn’t any link?????. Google sucks at getting any download links for this tool (Ã²_Ã“). See to believe…

GM never alters your code. It should. Maybe if I get time and nobody releases an obfuscator, I could make one. Most likely I wont, since that would involve using Zach’s poorly programmed GMK library (torll).

Decompilers can be great learning tools. We all should know how beneficial working source code is to a starting programmer. If anyone wanted to ‘steal’ code through it the chances of it fitting perfectly with their architecture are slim – and other resources are so obvious when stolen that I don’t think they would get far.

I would still be really thankful for whoever makes an obfuscator though 😛

We (the x2048 guys) have actually urged Charlie to update his Anti Decompiler (because we feel that if somebody truly wants to protect their game, they can, but we also wanted to provide a tool to recover game sources in the case of an accident, etc.), but he has no interest in it. There are a few individuals who are working on writing their own anti decompiler solutions, so maybe you didn’t waste your cash.

Not trolling, just having fun. And honestly I try to keep the tool up to date somewhat because I’ve seen it used for legitimate reasons. I’ve asked Charlie to update his anti-decompiler tool but he cbf’d to.

Plus, this is still pointing out security flaws in GM, although YYG’s has done a pretty good job with GM since 8.1.

Unfortunately, even if YoYo does keep tweaking the EXE format to keep one step ahead of decompilers, it won’t be of any use to a game that’s already been released and has lots of copies out there on the internet. They can’t all be called back in for recompiling.

Does anyone know if GM 8.1 at least obfuscates the source code, such as removing comments, changing variable names, etc? That would be a pretty easy thing to do and it would at least prevent people from getting usable source code.

I guess if someone is just planning on copying your game outright without making any changes (other than the credits), then obfuscating doesn’t make much a difference. But at least in that case, the copy of your work is easier to spot because its identical.

I do think looking at code is a valuable way to learn, but I also think it should be up to the author whether to release their source code or not.